A mold for use at an injection molding machine is ordinarily provided with plural cavities in a parting line (PL) plane thereof for the purpose of producing a number of molded products.
When plural forms are required to be prepared using a mold having cavities formed therein, a different mold must be prepared for each form, that is, plural molds must be prepared for the required forms. This causes the overall cost to be increased. In order to overcome the above disadvantage, there has been proposed a technique in which plural sub-molds each having cavities are prepared, one of the prepared sub-molds is selected in accordance with a required form and then the selected sub-mold is inserted into a common mold. When a sub-mold is exchanged for another one in this technique, the entire mold is removed from a molding machine while suspending the mold with a crane or the like, and then a sub-mold accommodated in the mold is exchanged for another one.
The removing operation of the entire mold causes a tremendous risk because the mold itself has a heavy weight. In addition, the removing operation itself requires a long time and many hands, so that the removing operation is obstacle to an automation of a series of injection molding processes.